Kristoffer Koch

Effect of Socioeconomic Status on Mortality after Bacteremia in Working-Age Patients. A Danish Population-Based Cohort Study

Objectives To examine the effect of socioeconomic status (SES) on mortality in patients with bacteremia and the underlying factors that may mediate differences in mortality. Methods We conducted a population-based cohort study in two Danish regions. All patients 30 to 65 years of age with first time bacteremia from 2000 through 2008 were identified in a population-based microbiological bacteremia database (n = 8,653). Individual-level data on patients’ SES (educational level and personal income) and comorbid conditions were obtained from public and medical registries. We used Cox regression to examine mortality within 30 days after bacteremia with and without cumulative adjustment for potential mediators. Results Bacteremia patients of low SES were more likely to live alone and be unmarried than patients of high SES. They also had more pre-existing comorbidity, more substance abuse, more Staphylococcus aureus and nosocomial infections, and more admissions to small nonteaching hospitals. Overall, 1,374 patients (15.9%) died within 30 days of follow-up. Patients of low SES had consistently higher mortality after bacteremia than those of high SES crude hazard ratio for low vs. high education, 1.38 [95% confidence interval (CI), 1.18–1.61]; crude hazard ratio for low-income vs. high-income tertile, 1.58 [CI, 1.39–1.80]. Adjustment for differences in social support, pre-existing comorbidity, substance abuse, place of acquisition of the infection, and microbial agent substantially attenuated the effect of SES on mortality (adjusted hazard ratio for low vs. high education, 1.15 [95% CI, 0.98–1.36]; adjusted hazard ratio for low-income vs. high-income tertile, 1.29 [CI, 1.12–1.49]). Further adjustment for characteristics of the admitting hospital had minimal effect on observed mortality differences. Conclusions Low SES was strongly associated with increased 30-day mortality after bacteremia. Less social support, more pre-existing comorbidity, more substance abuse, and differences in place of acquisition and agent of infection appeared to mediate much of the observed disparities in mortality.

International travel and the risk of hospitalization with non-typhoidal Salmonella bacteremia. A Danish population-based cohort study, 1999-2008

BackgroundInformation is sparse regarding the association between international travel and hospitalization with non-typhoidal Salmonella bacteremia. The aim of this study was to determine the proportion, risk factors and outcomes of travel-related non-typhoidal Salmonella bacteremia.MethodsWe conducted a 10-year population-based cohort study of all patients hospitalized with non-typhoidal Salmonella bacteremia in three Danish counties (population 1.6 million). We used denominator data on Danish travellers to assess the risk per 100,000 travellers according to age and travel destination. We used patients contemporaneously diagnosed with travel-related Salmonella gastroenteritis as reference patients to estimate the relative risk of presenting with travel-related bacteremia as compared with gastroenteritis. To evaluate clinical outcomes, we compared patients with travel-related bacteremia and patients with domestically acquired bacteremia in terms of length of hospital stay, number of extraintestinal focal infections and mortality after 30 and 90 days.ResultsWe identified 311 patients hospitalized with non-typhoidal Salmonella bacteremia of whom 76 (24.4%) had a history of international travel. The risk of travel-related bacteremia per traveller was highest in the age groups 15-24 years (0.8/100,000 travellers) and 65 years and above (1.2/100,000 travellers). The sex- and age-adjusted relative risk of presenting with bacteremia was associated with travel to Sub-Saharan Africa (odds ratio 18.4; 95% confidence interval [6.9-49.5]), the Middle East (10.6; [2.1-53.2]) and South East Asia (4.0; [2.2-7.5]). We found high-risk countries in the same three regions when estimating the risk per traveller according to travel destination. Patients hospitalized with travel-related bacteremia had better clinical outcomes than patients with domestically acquired bacteremia, they had a shorter length of hospital stay (8 vs. 11 days), less extraintestinal focal infections (5 vs. 31 patients) and a lower risk of death within both 30 days (relative risk 0.2; [0.1-0.7]) and 90 days (0.3; [0.1-0.7]). A healthy traveller effect was a plausible explanation for the observed differences in outcomes.ConclusionsInternational travel is a notable risk factor for being hospitalized with non-typhoidal Salmonella bacteremia and the risk differs between age groups and travel destinations. Healthy travellers hospitalized with bacteremia are less likely to have poor outcomes than patients with domestically acquired bacteremia.

The effect of community-acquired bacteraemia on return to workforce, risk of sick leave, permanent disability pension and death: a Danish population-based cohort study

Objectives Little is known about the prognosis of community-acquired bacteraemia (CAB) in workforce adults. We assessed return to workforce, risk for sick leave, disability pension and mortality within 1 year after CAB in workforce adults compared with blood culture-negative controls and population controls. Design Population-based cohort study. Setting North Denmark, 1996–2011. Participants We used population-based healthcare registries to identify all patients aged 20–58 years who had first-time blood cultures obtained within 48 h of medical hospital admission, and who were part of the workforce (450 bacteraemia exposed patients and 6936 culture-negative control patients). For each bacteraemia patient, we included up to 10 matched population controls. Primary and secondary outcome measures Return to workforce, risk of sick leave, permanent disability pension and mortality within 1 year after bacteraemia. Regression analyses were used to compute adjusted relative risks (RRs) with 95% CIs. Results One year after admission, 78% of patients with CAB, 85.7% of culture-negative controls and 96.8% of population controls were alive and in the workforce, and free from sick leave or disability pension. Compared with culture-negative controls, bacteraemia was associated with an increased risk for long-term sick leave (4-week duration, 40.2% vs 23.9%, adjusted RR, 1.51; CI 1.34 to 1.70) and an increased risk for mortality (30-day mortality, 4% vs 1.4%, adjusted RR, 2.34, CI 1.22 to 4.50; 1-year mortality, 8% vs 3.9%, adjusted RR, 1.73; CI 1.18 to 2.55). Bacteraemia patients had a risk for disability pension similar to culture-negative controls (2.7% vs 2.6%, adjusted RR, 0.99, CI 0.48 to 2.02) but greater than population controls (adjusted RR, 5.20; 95% CI 2.16 to 12.50). Conclusions CAB is associated with long duration of sick leave and considerable mortality in working-age adults when compared with blood culture-negative controls, and an increased 1-year risk for disability pension when compared with population controls.

Socioeconomic Inequalities in Risk of Hospitalization for Community-Acquired Bacteremia: A Danish Population-Based Case-Control Study

In a Danish population-based case-control study, we examined the association between socioeconomic status (SES) and risk of community-acquired bacteremia, as well as the contribution of chronic diseases and substance abuse to differences in bacteremia risk. Analyses were based on 4,117 patients aged 30-65 years who were hospitalized with first-time community-acquired bacteremia during 2000-2008 and 41,170 population controls matched by sex, age, and region of residence. Individual-level information on SES (education and income), chronic diseases, and substance abuse was retrieved from public and medical registries. Conditional logistic regression was used to compute odds ratios for bacteremia. Persons of low SES had a substantially higher risk of bacteremia than those of high SES (for short duration of education vs. long duration, odds ratio = 2.30 (95% confidence interval: 2.10, 2.52); for low income vs. high income, odds ratio = 2.77 (95% confidence interval: 2.54, 3.02)). A higher prevalence of chronic diseases and substance abuse in low-SES individuals versus high-SES individuals explained 43%-48% of the socioeconomic differences in bacteremia risk. In a country with a universal welfare system, differences in the burden of chronic diseases and substance abuse seem to have major importance in explaining inequalities in bacteremia risk.